1. Field of the Invention
The present invention relates to group key management, and in particular, to a method and apparatus for effectively updating a group key in a group including mobile devices.
2. Description of the Related Art
In an environment where there are a plurality of device groups, what is the most important thing among security issues in communication between devices is to prevent a device that does not belong to a group from acting as a member of the group and receiving a multicast message which is transmitted only to devices which belong to the group.
In order to reduce the burden in operation and communication of a server, a multicast message transmitted to a group is encrypted with a group key. In addition, when a user of the group is changed, the group key should be updated in order to prevent the user from viewing the multicast message before subscribing to the group or after withdrawing from the group.
A fixed device directly receives an updated group key from a predetermined key distribution center or a base station.
However, when a device is moveable, not only the device should receive a group key in a wireless manner but also a base station for transmitting the group key may be changed in each case. Therefore, security for the group key may be insufficient. In addition, there is a problem that a mobile device is not able to receive a group key when a communicable base station is not located near the mobile device.